firmware: tegra: Make TEGRA_IVC a hidden Kconfig symbol

kconfiglint reports:

  K002: config TEGRA_BPMP selects visible symbol TEGRA_IVC which has
        dependencies

TEGRA_IVC was originally introduced in
commit ca791d7f42 ("firmware: tegra:
Add IVC library") as a user-visible
bool with a prompt ("Tegra IVC protocol"). At that time, TEGRA_BPMP
depended on TEGRA_IVC, requiring users to manually enable it.

Recently,
commit 78eb18020a ("firmware: tegra: Fix IVC dependency problems")
recognized that TEGRA_IVC is library code that should be activated via
`select` rather than user selection. That commit changed TEGRA_BPMP from
`depends on TEGRA_IVC` to `select TEGRA_IVC`, and restricted TEGRA_IVC's
prompt to only appear under COMPILE_TEST
(`bool "Tegra IVC protocol" if COMPILE_TEST`). The commit message
explicitly states: "The IVC code is library code that other drivers need to
select if they need that library."

However, the `if COMPILE_TEST` qualifier still leaves TEGRA_IVC as a
technically visible symbol, triggering K002 when TEGRA_BPMP selects it.
Since TEGRA_IVC depends on ARCH_TEGRA, it cannot be independently enabled
under COMPILE_TEST without ARCH_TEGRA anyway, limiting the value of the
standalone COMPILE_TEST path. TEGRA_BPMP itself provides adequate
COMPILE_TEST coverage for the IVC library through its own dependency chain.

Complete the transition to a pure library symbol by removing the prompt
entirely, making TEGRA_IVC a hidden bool activated only via select from
TEGRA_BPMP. This is consistent with the intent expressed in 78eb18020a.

Assisted-by: Claude:claude-opus-4-6 kconfiglint
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/firmware/tegra/Kconfig

@@ -2,7 +2,7 @@
 menu "Tegra firmware driver"
 
 config TEGRA_IVC
-	bool "Tegra IVC protocol" if COMPILE_TEST
+	bool
 	depends on ARCH_TEGRA
 	help
 	  IVC (Inter-VM Communication) protocol is part of the IPC